- date_create_from_format: documentation ( source)
<?php
$settings['started'] = 342534534;
$started = date_create_from_format('U', $settings['started']);
echo $started->format('Y-m-d H:i:s') . PHP_EOL;
$started->sub(new DateInterval('PT2M'));
echo $started->format('Y-m-d H:i:s') . PHP_EOL;
$started = date_create_from_format('U', $settings['started']);
echo $started->format('Y-m-d H:i:s') . PHP_EOL;
$started->modify('-2 minutes');
echo $started->format('Y-m-d H:i:s') . PHP_EOL;